BOSTON -- School, MBTA and other diesel buses that idle for illegally long periods of time in Boston are creating an unhealthy environment for city residents, and particularly its children.

NewsCenter 5's Janet Wu reported Sunday that Boston has the third highest level of diesel pollution in the country. Statewide, it leads to more than 450 premature deaths, 700 heart attacks and nearly 10,000 asthma attacks each year. The biggest source is trucks and buses.

They line up in front of schools every morning, then again in the afternoon. They often sit there idling for as long as 25 minutes. But state law is clear: if you expect a more than five minute wait, turn off the engine or face a hefty fine.

Team 5 Investigates randomly monitored several schools over several days. Rarely did these buses shut down.

“I notice you've been idling here for quite a while,” Wu said to one school bus driver.
“Waiting for kids,” he replied.
“But you're not supposed to idle for more than five minutes.”

The driver repeated that he was waiting for kids and then closed his window in Wu's face and waved her off.

These drivers know they're supposed to kill the engines. A statewide education campaign was completed last year. Once these drivers spotted our camera, they immediately shut down.

Wu asked to another school bus driver, “Your bus was idling until you saw my camera. How come?”
Driver: “I just come in here. Three minutes since I came here.”
Wu: “We saw you for more than three minutes.”
Driver: “No.”

The fumes from these illegally idling buses pose a health risk to children.

“You notice the pipes, the exhaust pipes, are at their breathing level,” said Jodi Sugerman-Brozan, of the group Alternatives for Community and Environment. “Diesel particulate matter is very dangerous. It's tiny, tiny little particles can get deep inside the lungs. Not only are they an irritant to the lungs that can cause asthma attacks but they also have over 40 kinds of chemicals attached to each tiny little particle. So it's a carcinogen.”

Parents and residents here in Hyde Park say their complaints may turn off the engines for one day. But the next day, they're idling again.

Parent Howard White said, “I think it's clearly dangerous. The fumes from these big diesel engines are constantly there. It's carbon monoxide for the most part so you can't really smell it.”

It's not just school buses violating the law. Delivery trucks and garbage trucks park for extended times with their engines running. Here at Dudley Station, many MBTA buses are powered by natural gas, but there are enough still running on diesel fuel to make it the state's number hot spot.

Sugerman-Brozan showed us machines in Roxbury that measure particulate matter in the air. “We're standing in a neighborhood where asthma rates are five to six times the state average. And, again, asthma is the number one reason kids are absent from Boston public schools”

State officials admit diesel pollution is a big problem in New England, particularly in Boston and most severely in Roxbury. They point to programs to retrofit all school buses by 2010, but that's three years away. And tens of thousands of diesel powered vehicles plow through Massachusetts on any given day.

David Cash, the Assistant Secretary of Environmental Affairs for Massachusetts said he didn’t know the exact number of violations that his agency handed out last year.

Wu: “Maybe hundreds?”
Cash: “I don’t think hundreds.”
Wu: “Much less?”
Cash: “Yeah.”

The state law is clear, 5 minutes of idling, no more. So who's enforcing it?

“Really nobody, really nobody at this point and it needs to be something that residents, and people within the school community start to take action and make decision makers accountable,” said Sugerman-Brozan.

State officials admit they and local police simply don't have the resources to man every school or bus station. They call on residents, parents and teachers to document violation: video, dates and times, then turn in the evidence. If drivers know they're being watched, they'll shut it down.